Methods for preparing inorganic compounds having a substantially single phase, hexagonal layered crystal structure that is substantially free from cubic-spinel like phases

Abstract

The present invention relates to compounds having a hexagonal layered structure that is substantially free from cubic-spinel like phases, a process for preparing the same and the use thereof.

1. A method of preparing a compound having a substantially single phase, hexagonal layered crystal structure and being substantially free of localized cubic spinel-like structural phases, the method comprising the steps of providing a lithium metal oxide having the formula Li x Ni a Co b Mn c O 2 , wherein a and c are independently of each other a number from 0.05 to 0.8, b is a number between 0.05 and 0.50, 0.95≦(a+b+c)≦1.02, and x being a number from 0.98-1.05 while x+a+b+c=2, at a temperature of at least about 600° C.; and cooling the lithium metal oxide at a cooling rate in which temperature is a function of time and is determined by a formula of T=f*EXP(−R*t), wherein T is the temperature in degrees centigrade, and t is the cooling time in minutes, wherein f is from 600° C. to 1000° C. and R is from 0.0009 to 0.01, and the function is non linear. 
     
     
       2. The method according to  claim 1 , wherein f is from 750° C. to 850° C. and R is from 0.001 to 0.009. 
     
     
       3. The method according to  claim 1 , wherein R is from 0.002 to 0.005. 
     
     
       4. The method according to  claim 1 , wherein R is from 0.003 to 0.0044. 
     
     
       5. The method according to  claim 1 , wherein said cooling step comprises uniformly cooling the Li x Ni a Co b Mn c O 2  compound. 
     
     
       6. The method according to  claim 1 , wherein said providing step comprises synthesizing the Li x Ni a Co b Mn c O 2  compound at a temperature of at least about 600° C. 
     
     
       7. The method according to  claim 1 , wherein said providing step comprising heating a previously-synthesized Li x Ni a Co b Mn c O 2  compound to a temperature of at least about 600° C. 
     
     
       8. The method according to  claim 1 , wherein b is a number between 0.05 and 0.45.